Internet drops for a few seconds at intervals of 30 minutes or multiples of 30 minutes

Hello,

I own my cable modem, a Netgear Nighthawk CM1150V. It's worked flawlessly since I activated it in June of 2020. Until now. I understand that Xfinity doesn't service customer-owned equipment, but I believe my trouble arises either in Xfinity's equipment or because of the most recent firmware update (ver 4.12.04) that Xfinity downloaded into my modem.

Starting about two months ago, my internet has experienced very regular interruptions, lasting 2 to 8 seconds. The interval between these outages is always a precise multiple of 30 minutes, for instance at 17 minutes and 47 minutes after the hour. Sometimes the trouble doesn't manifest every time 30 minutes rolls around, but when the trouble returns, the interruptions are still on the same schedule. Rebooting the modem doesn't solve the problem, but causes the time of the service interruptions to shift; the next outage happens 30 minutes after the reboot, and then at 30 minute intervals after that.

When my son alerted me to this problem I checked the modem's logs. No events had been logged for the last two days; days during which the service interruptions had continued to happen. So the interruptions either aren't originating in the modem, or aren't a type of event that the modem logs.

I eliminated the router as a suspect by having my son connect his PC directly to the modem as he gamed online. (The interruptions are short enough that they aren't noticable during browsing, nor during streaming due to content spooling; but the sudden freeze is irritating on Zoom calls and is disasterous for game combat.) With my son's PC connected directly to the modem's ethernet port, and nothing else connected to the modem except the power and Xfinity's coax cable, the interruptions continued apace.  That eliminates the LAN, including the router, as cause of the service interruptions.

On March 11 I used the modem's pinhole button to reset it to factory specs. Then I followed Xfinity's instructions at

     https://www.xfinity.com/support/articles/activate-voice-gateway-modem

to activate the like-new modem. I hoped that if some value had gotten set wrong in the switch's provisioning data for my connection, the activation process for a new modem would populate it with the standard values.

It didn't help. My internet connection still freezes for a few seconds at intervals that are multiples of 30 minutes.

 

I can offer one lead: Xfinity has dealt with this exact same problem before. I searched online for descriptions of my problem, and one of the top hits was right on this Xfinity forum:

     https://forums.xfinity.com/conversations/your-home-network/dropped-connection-every-30-minutes-precisely/6241f2b6f6cc380e6401baff

That forum conversation started March 28th, 2022 and continued until sometime in October, with some additional customers adding that they had the same problem. The conversation is marked "closed." Unfortunately, no resolution of the problem is described. Maybe Xfinity's service department opened a corresponding trouble ticket which led to the problem being fixed, and none of those customers ever logged back into the forum to say so and to say thanks. So maybe your service department already has the solution to my problem, in a now-closed trouble ticket that was opened on or shortly after 3/28/2022.

I also offer a suggestion: If the problem is somehow caused by the most recent firmware download that Xfinity put into my modem, then downloading the previous version may fix the problem. If it does fix the problem, then the fix would also pinpoint the cause of the problem.

There are other Xfinity customers with the Netgear CM1150V modem. They could all be experiencing these very short internet interruptions ever since the latest firmware download, yet few would notice because it isn't apparent during browsing, shopping, or streaming; only during Zoom-type calls and gaming. Netgear won't learn about the problem from any other ISP, because the CM1150V was developed in colaboration with Xfinity and is deployed only or primarily on Xfinity's network. I cannot revert my own modem to the previous firmware version to test my theory, because Netgear provides the firmware only to Xfinity. So if there's a bug in the current firmware release, only Xfinity is in a position to confirm it, to inform Netgear of it, and hopefully, to restore constancy to my internet connection.